S.C. Code § 38-25-540
An unauthorized insurer is not permitted to maintain any action, suit, or proceeding in this State to enforce a right, claim, or demand arising out of the transaction of insurance business until the insurer has obtained a certificate of authority to transact insurance business in this State. The unauthorized insurer may maintain an action, suit, or proceeding in connection with its investments in this State or in connection with a contract issued by it at a time when it was authorized to do business in the state where the contract was issued. This section does not prevent the insurer from defending an action in the courts of this State. The failure of an insurer transacting insurance business in this State to obtain a certificate of authority does not impair the validity of any act or contract of the insurer. This section does not apply to an eligible surplus lines insurer which maintains the deposit required by Section 38-9-80 or which has on file with the department a surety bond issued by an admitted insurer in an amount determined by the director or his designee to be sufficient to meet the security requirements of Section 38-9-80. Before an eligible surplus lines insurer files or causes to be filed any action, suit, or proceeding in this State to enforce a right, claim, or demand arising out of the transaction of insurance, it shall produce evidence that the security deposit is presently on file or that the required surety bond is then in force and effect.
S.C. Code § 38-25-540